Dartdoc should sort constructors by constructorName, not by class name

Dartdoc should sort constructors by constructorName, not by class name
Committed: https://code.google.com/p/dart/source/detail?r=13139

[Alan Knight, 2012-10-02 20:54:08]

The current version sorts by simpleName, which for a constructor is just the
class name.

[Emily Fortuna, 2012-10-02 20:56:35]

lgtm